Reliable performance of electronic devices depends primarily on the integrity of the microelectronic components contained therein. Most electronic devices contain several microchips which are housed in a variety of protective packages. These packages are composed of several distinct materials, each of which performs a specific function and contributes to the overall integrity of the package. For example, a typical ball-grid array (BGA) package contains, in addition to the substrate and microchip attached thereto, materials such as overmold adhesive, die-attach adhesive, and solder mask. The incorporation of all of these disparate materials into one package creates several adhesive interfaces within the package itself. In order to produce a reliable, long-lasting electronic device, the structural integrity of these interfaces must be maintained.
Interfacial adhesion is a critical parameter for the production of reliable microelectronic components. Materials with dissimilar coefficients of thermal expansion must be adhered via void-free bonds. The presence of any delamination in the final assembled product can lead to moisture entrapment within the void volume. The trapped moisture can be released “explosively” once the defective part is heated to solder reflow temperatures during final component assembly. The formation of sound adhesive bonds at the various interfaces present within a microelectronic package is therefore critical for the survival of that package during assembly. The formation of sound adhesive bonds is also necessary to insure a long service life for the final product.
Adhesive interfaces within electronic components are currently subjected to increasingly stringent processing conditions. For example, environmental concerns have resulted in a worldwide mandate to remove lead from all aspects of the microelectronic assembly process. The use of lead-free solder alloys, however, creates a new challenge for the reliable assembly of microelectronic components. The reflow temperatures required by lead-free alloys are several degrees higher than those containing lead. Soldering operations based on these new alloys generally must be conducted around 260° C., which is about forty degrees Celsius higher than had been previously required. The new, higher reflow temperatures place an extra strain on all of the adhesive interfaces within microelectronic packages. Indeed, strong adhesion at all of these interfaces is critical to the reliability of a microelectronic component.
Benzoxazines and compositions containing benzoxazines are known (see for example, U.S. Pat. Nos. 5,543,516 and 6,207,786 to Ishida, et. al.; S. Rimdusit and H. Ishida, “Development of New Class of Electronic Packaging Materials Based on Ternary Systems of Benzoxazine, Epoxy, and Phenolic Resins”, Polymer, 41, 7941-49 (2000); and H. Kimura, et. al., “New Thermosetting Resin from Bisphenol A-based Benzoxazine and Bisoxazoline”, J. App. Polym. Sci., 72, 1551-58 (1999)). However, benzoxazines have generally not been used as components of thermosetting resin compositions to increase the interfacial adhesion thereof.
Accordingly, there is a need for compositions and methods which increase interfacial adhesion within microelectronic components.